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UBC Theses and Dissertations

Effect of vacuum microwave dehydration on the off-flavour intensity and functionality of pea proteins Yen, Philip Pui-Li


Pea (Pisum sativum L.) has garnered recent attention as a plant-protein source due to its high protein content, nutrient density and low allergenicity. However, pea proteins are difficult to incorporate into food formulations due to undesirable green, grassy and beany aromas and limited functional properties. Direct steam injection is often used in the food industry to decrease off-flavour intensity of pea proteins and improve functional properties. However, induced cooked off-flavours and nutrient losses that are attributed to heating warrant exploration of an alternative process. This research examined the applicability of vacuum microwave dehydration as a pre-processing step for plant protein for use during non-dairy alternative production. In this thesis, effects of the following process parameters: initial moisture content (5-425% dry basis), vacuum level (40-200 Torr), specific power (10-200 W/g), and process time (1-50 minutes) on volatile compound concentration, functionality and quality parameters such as available lysine and colour, were analyzed. Increasing initial moisture content decreased (p<0.05) protein solubility, emulsifying activity index and chemically available lysine content, but increased (p<0.05) emulsifying stability index. Having a higher initial moisture content decreased (p<0.05) lightness, but increased (p<0.05) the a* and b* coordinates and total colour difference compared to untreated pea protein. Generation of specific volatiles related to thermally induced lipid oxidation was observed in some samples, thus, necessitating lower specific energy treatments to be considered. Results showed that three VMD processes could be developed for use on two sources of pea proteins. VMD-processing pea protein with an initial moisture content of 162% d.b. at 100W/g microwave energy and 200 Torr vacuum-level for 2.5 minutes was found to be the optimal conditions for retaining functional properties and minimizing volatile concentration that contributed to off-flavour intensity. Descriptive analysis showed that the finalized VMD-process reduced levels of “raw/beany” and “green/grassy” aroma and flavour, but increased overall aroma intensity, “goaty/caproic acid” aroma and “chalky flavour”. Future consumer trials are needed to verify whether these differences in attribute intensities are relevant at the consumer level.

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